The limestone cavern of the city was dome shaped and more than two miles in diameter. A shallow lake lies in the center of the cavern was fed by two freshwater rivers and drained by a third. The rivers left large plateaus upon which the drow dwelt; slaves often dwelt in caves along the shores of the lake.[1]

The city's three plateaus were each dominated by one of three religious cults: Lolthites held the largest plateau, located on the western side of the city. Vhaeraunites dwelt on the northeastern plateau, and the southeastern plateau (which was often flooded) was home to followers of Ghaunadaur.[1]

Eryndlyn was founded by drow seeking to reclaim the ancient elven realm of Miyeritar. They were not particularly religious, so unlike many other drow cities, Eryndlyn was not devoted to one particular deity. However, as merchant clans grew to dominate the leadership of the city, cults to Ghaunadaur, Lolth, and Vhaeraun sprang up in an attempt to gain power. Each cult eventually consolidated their followers to one of the plateaus.[1]

The Jaezred Chaulssin established a hidden fosterage in the city.[5] During the Silence of Lolth (1372-1373 DR) the members of Jaezred Chaulssin brought the worshipers of Vhaeraun and Ghaunadaur together and helped to unite them against the weakening worshipers of Lolth.[6][7] They decimated the followers of the Spider Queen drastically, leaving the western plateau in ruins.[8]

The followers of Kiaransalee attempted to gain a foothold in the city, but as of 1372 DR they had counted a few outlaw drow among their number.[8]

The Spellplague destroyed Eryndlyn, leaving it a blasted ruin. Duergar from Gracklstugh began reporting earthquakes and explosions from the ruin in the area adjoining the city known as the Spellcaves - a cavern full of wild magic since Eryndlyn's destruction. Lolth, in the form of Danifae Yauntyrr, tried to use the Spellcaves as a focus to merge herself with the Demon Weave in 1485 DR, thereby becoming the new goddess of arcane magic, but the attempt failed and instead Mystra, thought dead for an entire century, appeared and warped the Demon Weave into a form more akin with her original Weave.[9]